Comparative study of anodizing and chromate conversion coatings in enhancing the wear and corrosion properties of 6063 Al alloy

Abstract

ABSTRACT The present study compares the corrosion and tribological performance of anodic oxide (AO) and chromate conversion (CC) coatings deposited on 6063-T6 aluminum alloy. The goal is to determine how these treatments benefit the performance of the underneath substrate. The corrosion protection properties of the coatings were evaluated by potentiodynamic polarization measurement in 3.5 wt. % NaCl solution. The friction and sliding wear behavior of coatings were studied by pin-on-disk test and their erosion behavior was examined by air jet solid particle erosion test. The surface structure, chemical composition, roughness, wettability, and hardness of specimens were also characterized. The results showed that the AO coating with porous surface morphology was found to be thicker, rougher, and harder along with greater wettability, when compared to CC coating. Furthermore, the AO coating with polarization resistance of 6.64 × 103 Ω.cm2 enhanced the corrosion resistance of the substrate more than 8 times. In addition, the AO coating under dry and wet sliding conditions reduced the aluminum alloy substrate wear rate by about 80% and 52%, respectively. However, due to being more brittle, the AO coating lost more weight than the CC coating during the solid particle erosion test.